SYNTHESES AND STRUCTURES OF CYCLOPENTADIENYL ARSENIC COMPOUNDS .2. PENTAMETHYLCYCLOPENTADIENYL AND TETRAISOPROPYLCYCLOPENTADIENYL ARSENIC AMIDO DERIVATIVES
Ev. Avtomonov et al., SYNTHESES AND STRUCTURES OF CYCLOPENTADIENYL ARSENIC COMPOUNDS .2. PENTAMETHYLCYCLOPENTADIENYL AND TETRAISOPROPYLCYCLOPENTADIENYL ARSENIC AMIDO DERIVATIVES, Journal of organometallic chemistry, 544(1), 1997, pp. 79-89
A series of amido derivatives of arsenic cyclopentadienyls (Cp'AsNR)(n
) (4-6) (4: Cp' = C5Me5, R = H, n = 4; 5: Cp' = C5Me5, R = Me; n = 2;
6: Cp' = C(5)i-Pr4H, R = Me, n = 2) has been synthesized by the reacti
on of Cp'AsX2 (1-2) (1: Cp' = C5Me5, X = Cl; 2: Cp' = C(5)i-Pr4H, X =
I) with an excess of amine. The reaction proceeds via a diamido substi
tuted intermediate which eliminates in vacuum one equivalent of free a
mine to give in situ imino arsanes which rapidly oligomerize to octa-o
r tetracyclic compounds in almost quantitative yield. In the case of b
ulky amines, viz. t-BuNH2 and (Me3Si)(2)NH, monoamido substituted arsa
nes CpAsCl((NRR2)-R-1) (7-8) (7: R-1 = H, R-2 = t-Bu; 8: R-1 = R-2 =
SiMe3) have been obtained by treatment of I with an excess of t-BuNH2
or with one equivalent of NaN(SiMe3)(2). The fluorine substituted anal
ogue of 8, CpAsF[N(SiMe3)(2)] (9), has been synthesized either by rea
ction of one equivalent of NaN(SiMe3)(2) with CpAsF2 (3) or by a subs
titution reaction between 8 and Cp2CoF in moderate yields. 7 reacts wi
th strong bases, e.g. Li(Na)N(SiMe3)(2) or Me3SnNEt2, giving an imino
arsane as an intermediate which quickly dimerizes to diazadiarsetane (
CpAsNt-Bu)(2) (10). The reaction of 1 with Ph2C=NNH2 in the presence
of Et3N as a base gives the disubstituted hydrazonato arsane CpAs(NHN
=CPh2)(2) (11), independent of the reagent ratio. All new compounds we
re characterized by spectroscopic methods (H-1, (CNMR)-C-13, MS) and e
lemental analyses. The crystal structures of 4-8 have been determined
by X-ray diffraction methods. Bonding of the arsenic fragment to the c
yclopentadienyl ligand can be described as a primary sigma-interaction
with an additional pi-interaction between the cyclopentadienyl ligand
and the arsenic atom, resulting in pseudo-eta(2) to eta(3)-coordinati
on. Short intramolecular As-As contacts are found for 5 and 6. (C) 199
7 Elsevier Science S.A.